class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) 
    {
        if(p == NULL && q == NULL)
            return true;

        if(p == NULL && q != NULL || p != NULL && q  == NULL)
            return false;

        if( p -> val == q -> val)
        {
            return isSameTree(p -> left, q -> left) && isSameTree(p -> right, q -> right);
        }
        else
            return false;
    }
};
